1. Technical Field
The present invention relates to polymer composite materials and more particularly to polymer composite materials used as abrasives and more particularly as a blast media. Still more particularly, this invention relates to the use of nano-structure composite materials as an abrasive and a blast media.
2. Background Information
Various methods and compositions are taught in the prior art for the stripping of organic coatings from an underlying metal or composite substrate by means of polymer abrasives. Such polymer abrasives have the advantage of being harder than the organic substrate but softer than the underlying substrate.
U.S. Pat. No. 4,731,125, for example, discloses a process whereby paint is removed from composites by blasting with urea-formaldehyde plastic particles having a Mohs scale hardness of 2.5–3.5 with a flow at a pressure of 40 lb/in2.
U.S. Pat. No. 4,947,591 discloses a process whereby paint is removed by impact with particles of an acrylic-containing unsaturated polyester where the particles are ground from a cured mass so as to have at least 40 facets per particle.
U.S. Pat. No. 5,112,406 discloses a process for removing coatings from sensitive hard surface metal composite surfaces, masonry, stucco, plaster or wood by blasting the surfaces with a high velocity fluid stream containing water soluble crystalline sodium sulfate particles admixed with a hydrophobic silica or hydrophobic polysiloxane flow/anti-caking agent.
U.S. Pat. No. 5,160,547 discloses a process where the surfaces are blasted with water saturated compressed air stream under pressures of 10–150 psi using sodium bicarbonate particles having particle sized of 250–300 microns in admixture with a hydrophobic silica flow/anti-caking agent.
U.S. Pat. No. 5,147,466 discloses fine particles or oil films which are cleaned from the surface by bombarding it with fine frozen particles of water or other liquids such as glycerin carried in a stream of nitrogen cooled air under relatively low pressure.
U.S. Pat. No. 5,221,296 discloses abrasives based on finely divided abrasive particles bonded to one another and/or to a support by means of a binder, where the binder is the solid component of an aqueous polymer dispersion which is obtainable by polymerizing unsaturated monomers which can be polymerized by means of free radicals in the aqueous phase of a monosaccharide, oligosaccharide, polysaccharide, oxidatively, hydrolytically and/or enzymatically degraded polysaccharide, chemically modified monosaccharide, oligosaccharide or polysaccharide or a mixture of the above.
U.S. Pat. No. 5,308,404 discloses a process by which contaminants are removed from substrates by blast cleaning with a media containing abrasive particles obtained by compacting fine particles of the abrasive into larger particles having a hardness of 2–5 Mohs and wherein the abrasive can be water (soluble or insoluble) and is preferably sodium bicarbonate or calcium carbonate.
U.S. Pat. No. 5,316,587 discloses blast cleaning a solid surface which includes the steps of propelling an abrasive blast medium against a solid surface using a water-containing pressurized fluid stream to strip contaminants from the surface wherein the blast medium comprises water soluble abrasive particles and a surfactant.
U.S. Pat. No. 5,322,532 discloses a process for removing contaminants from a substrate comprising blast cleaning the substrate with composite abrasive particles formed by agglomerating particles of sodium bicarbonate with a aqueous binder solution of sodium carbonate.
U.S. Pat. No. 5,360,903 and U.S. Pat. No. 5,367,068 disclose a process whereby a surface is treated with particles of a glassy polysaccharide wherein the apparent hardness of the granules is between that of the coating and of the substrate and the granules are of starch, preferably wheat starch with dextrose equivalent less than 10, preferably unhydrolyzed.
U.S. Pat. No. 5,380,347 discloses a blast media for stripping contaminants from a solid surface comprising abrasive particles and a surfactant in the form of a granular surfactant-clathrate compound formed of a surfactant and a water soluble compound having clathration capability such as urea. The surfactant reduces the amount of water-soluble residues, which remain on the targeted surface and enhances the removal of dirt, grease and oil from the targeted surface.
U.S. Pat. No. 5,427,710 discloses a composition useful for removing polymeric coatings from flexible and inflexible surfaces which consists essentially of a conjugated terpene, an alcohol, a non-conjugated terpene, a surfactant and an organo-clay rheological additive.
U.S. Pat. No. 5,780,619 discloses a starch graft poly(meth)acrylate blast media which is effective in paint removal. The media is superior to a physical blend of the components (i.e., starch and acrylic polymers) and to wither a starch polymer or an acrylic polymer used singly. The hardness of the media is between 65–90 Shore D.
A need, however, exists for ways to improve the speed and effectiveness of such stripping procedures. A need also exists for ways of decreasing the breakdown rate of abrasives used for this purpose.